Backing up data is a process that generates a coherent copy of data. Backing up data has become more important as the amount of data has exploded in volume and the importance of electronic records has also greatly increased. Backups are performed for various reasons, such as to assure availability of data, to generate data archival, or to transport data to a distant location.
Many schemes have been developed to generate backup data. One data backup scheme is to generate point-in-time (PIT) copies of data. PIT copies which are generated are either hardware-based or software-based. A hardware-based PIT copy is a mirror of a primary volume which has been saved onto a secondary volume. A software-based PIT copy, called a “snapshot,” is a “picture” of a volume at the block level or a file system at the operating system level. Another data backup scheme is where a backup application sends full or incremental copies of data to tape.
Backup data is generated in accordance with a data backup policy. Backup copies are generated and stored in a storage media, and maintained for a certain period of time. Often, not only is a single copy generated, but multiple copies of one original data are generated and maintained in separate media. Because of regulatory requirements, companies have to keep certain backup copies for several years. Accordingly, the data backup policy typically sets an expiration time for each backup data. For example, a system may retain daily snapshots or backups for two months, weekly snapshots or backups for two years and monthly snapshots or backups for seven years. Once the expiration time has passed, the backup copies are deleted completely from record, and should not be available in the future.
Historically, magnetic tape has been used as the storage medium for backing up data because tape has been a much cheaper medium than a disk. In order to completely delete backup data stored in a tape, a system operator typically needs to access each tape through the backup application, delete the backup data in question, and run another backup procedure on the tape. This is a labor-intensive and expensive process. This is even more complicated if only certain pieces of data on the tape need to be expired or if the tape can not be easily located.
One problem with these prior art scenarios is that even after the expiration time, many copies across many tapes are not deleted completely and are still in existence. This may cause a problem. For example, when critical data that should have been deleted is obtained by an adversary in a lawsuit, this may cause a tremendous damage to companies.
Therefore, there is a need to efficiently and completely delete all expired data from record in a way that it is no longer recoverable. This is the case even when it is not easy to obtain direct access to the data.